It is known to use rotatable dials to index workpieces in and out of processing stations, such as laser drilling stations, where precise control over the location of the workpiece is required. The dial is typically circular and has a central, vertical axis of rotation, referred to as the “Z-axis”. A motor is mounted in a frame below the table for indexing the table on command. The frame typically includes a dimensionally-stable surface underlying the table.
In conventional rotary indexers, the mass of the dial is supported by bearings of the indexer motor bearings. To protect the dial against out-of-plane excursions; large, expensive and highly precise indexer motor bearings are required so as to minimize play in the thrust direction; i.e., along the axis of rotation, and in tipping or tilting as a result of radial play. In the case of large diameter dials; i.e., dials of one meter or more in diameter, expensive measures have been taken to prevent tipping or tilling when vertical forces are applied near the outer edge of the dial. The measures include increasing the size of the indexer thrust bearings and adding outrigger structures that engage the dial when in an indexing location. Larger thrust bearings add cost, and the outriggers consume processing time and can cause positional errors.